Not sure. most of my stuff is 431, and a 432, but cant say i have looked to hard for the b stuff, but IIRC they did a few more 360 for the b then the A, or was it the other way round. Any how... was the frame here or did you bring it in ? if it was ex US id say its probally in a FT or something as they still turn up. If it was ex AU then you would be right it sitting in the corner of a garden somwhere rusting if not ina dumpster from a house clean. I can think of 3 other 360 frames and also the one i think its 090 has in Qld so there are at least 4 or more 360 motors out there that never came home.......... you might have to pick up an RT1 donk until you can find one, rarely you see BLANK side cases, but i have only seen 250cc in those, but surely they did a few replacement cases for the 360, if you can find one of them id say thats as good as matching numbers, but then you still need to fing the other bits to get it into spec, crank, clutch, straight cut gears etc, and the barstard part is not a lot of the 250 fits in the 360, it was a bit out on its own. Wiseco dont even make the pistons, so unless someone else did its Gen or nothing.
What Pistons are you using Ross ? and did you sleeve back to a cast barrell and move onto the MX360 pistons or trying to chase chrome ones still ?